Process for reactivating a rhodium trichloride catalyst



United States Patent "Ice 3,152,195 PROCESS FOR REACTIVATIN G A RHGDTUM TRICHLORIDE CATALYST John 3. Verbanc, Wilmington, Del, assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Apr. 10, 1961, Ser. No. 101,680 8 Claims. (Cl. 260680) This invention is directed to an improvement in the preparation of acyclic hydrocarbon dienes by condensing ethylene or propylene with 1,3-butadiene in the presence of a rhodium trichloride catalyst, wherein the catalyst is reactivated by treatment with hydrochloric acid and, optionally, with ethanol.

Acyclic hydrocarbon dienes are starting materials for valuable polymeric compositions. They can be prepared by condensing monoenes, such as ethylene or propylene, with conjugated acyclic hydrocarbon dienes in the presence of a rhodium trichloride catalyst. It has been found that during the process the catalyst becomes deactivated and is not eftective for further use. Unless some means can be used to reactivate the catalyst, the process becomes economically unfeasible.

It is, therefore, an object of this invention to provide a method whereby the herein described rhodium trichloride is reactivated after being utilized to condense monoenes with conjugated acyclic hydrocarbon dienes.

These and other objects Will become apparent in the following description and claims.

More specifically, the present invention is directed to the preparation of acyclic hydrocarbon dienes having 6 to 7 carbon atoms by condensing ethylene or propylene with 1,3-butadiene in the presence of a rhodium trichlon'de catalyst, the improvement being that which comprises reactivating the resulting used catalyst by adding at least one mole of hydrochloric acid per mole of rhodium trichloride catalyst initially charged, to the catalyst residue obtained after removal of the diene and before reuse of said catalyst.

A preferred embodiment of this novel process is that wherein ethanol is also added to the catalyst residue.

The process in which the catalyst residue is to be reactivated in accordance with the present invention involves the reaction of ethylene or propylene with 1,3- butadiene to yield hexadienes or methylhexadienes. When ethylene is reacted with butadiene, the product is predominantly 1,4-hexadiene with a smaller amount of 2,4-hexadiene. When propylene is reacted with butadicue, the product is predominantly 2-methyl-l,4-hexadiene.

The reaction desired is the equimolecular reaction of the monoene with butadiene. However, the molar ratio of reactants in the reaction vessel at any instant may vary depending on the manner in which the process is carried out. Both reactants may be charged to the reaction vessel, continuously or batchwise, in approximately equimolar amounts. It is preferred, however, to have a slight molar deficiency of the monoene present in the reaction system since the monoene is more reactive with itself and with the reaction product than is the butadiene. Alternatively, one of the reactants, preferably the butadiene, may be charged to the reaction vessel, and the other reactant may be fed to the vessel during the course of the reaction until the desired conversion is attained.

For the initial use of the rhodium trichloride catalyst, it is necessary that the solid catalyst be dissolved in a liquid in order to provide a homogeneous reaction medium. It is preferred to use the trihydrate of the rhodium trichloride because of its ready solubility in solvents. The preferred solvent is ethanol, Which may be aqueous or anhydrous. It is preferred to use absolute ethanol or the conventional 95 percent ethanol. The

3,152,195 Patented Oct. 6, 1964 quantity of ethanol used to dissolve the rhodium trichloride trihydrate is not critical except that a sufiicient amount should be used to dissolve the inorganic material. It is usually sufiicient to use 25 to 30 ml. of percent ethanol to dissolve 1 gram of rhodium trichloride trihydrate.

Only catalytic amounts of rhodium -trichloride are used. The concentration of rhodium trichloride required depends on such variables as the residence time in the reactor, the temperature used, and the conversion desired. Amounts as low as 0.000005 mole of catalyst per mole of starting material (monoene plus butadiene) are effective. Usually not more than 0.01 mole of catalyst per mole of starting material is required. The preferred range is from 0.00001 to 0.0005. In the catalyst concentration below 0.00001 it may be desirable to add hyrochloric acid to the initial run.

The reaction medium consists of the butadiene, which is liquid at the pressures and temperatures used, containing the ethylene or propylene dissolved therein.

The process may be carried out at pressures in the range of from about to about 700 p.s.i.g. This represents a practical range of pressures for generally available reactors. Higher or lower pressures may he used, if desired.

The process is carried out at temperatures in the range or" about 50 C. to about 100 C. At temperatures below 50 C., the reaction proceeds too slowly to be practical. Temperatures above 100 C. may be used, but are not generally required. The preferred range is between 60 C. and 100 C.

The time required for reaction depends on the temperatures and pressures used, catalyst concentration, de gree of conversion desired, and reactivity of the reactants. The practical range is from about 15 minutes to about 2 hours when ethylene and butadiene are reacted. When propylene is reacted with butadiene, up to 8 hours may be required since propylene is less reactive than ethylene.

In carrying out the herein described process by a batch process, a pressure reactor is charged with the catalyst solution. The reactor is then cooled, evacuated, and the diene compound is added. Agitation is begun, and ethylene or propylene is added. The reactor is then heated to the desired temperature and maintained at the desired temperature for sufficient time for the reaction to proceed to the desired conversion. At the end of the reaction time the autoclave is cooled to room temperature, and the contents are discharged; volatile prodnets are then stripped. The crude product is separated from the catalyst residue by distillation. The catalyst residue which remains is a liquid of unknown composition. In addition to the rhodium trichloride initially charged, it contains by-products from the reaction, probably of polymeric nature. To this catalyst residue is added the desired amount of hydrochloric acid and, optionally, ethanol. The resulting composition is used as the catalyst for the next reaction run.

At least one mole of hydrochloric acid per mole of rhodium trichlon'de originally charged is required to re activate the catalyst. Less than this amount gives insuffioient reactivation. Any amount of hydrochloric acid in excess of this may be used. There is no advantage to be gained in usin more than 40 moles of hydrochloric acid. The preferred range is 1.5 to about 15 moles of hydrochloric acid per mole of rhodium trichloride. The hydrogen chloride should be added as the aqueous acid, preferably as concentrated (37 percent) hydrochloric acid. The acid added may be more dilute, if desired, but there is no advantage to be gained by adding more dilute acid.

It has been found that the reactivating effect of the hydrochloric acid can be enhanced by the concomitant addition of ethanol to the catalyst residue. The quantity i l t f a li d b i ht A it ti i begun d of ethanol is not critical since as little as 500 grams per ethylene i chg ged by ressurefrom a cylinder by weight. mole of rhodium trichloride will afiord some added re- Subsequently, the gas inlet is sealed and heating is begun activating eff t h pr f amount Tangss {T0111 with a steam-water mixture in the jacket to attain and abl1i990 grams 502113011? 25,990 grams P 111016 of hold a desired temperature range. The reaction time is um trichloride. A greater amount of ethanol may be taken as period from time when the temperature reaches used, but there is no advantage to be gained. The ethanol 60 C til h li Water i li d,

may be anhydrous or aqueous. It is preferred to use 95 At the end of the reaction time, the autoclave is cooled percent ethanol. to 2530 C. and the contents are discharged by pressure T addition of hydrogen Chloride and, p y, from the discharge leg into a container. The volatile ethanol, to the catalyst after each run makes possible the products are stripped oil using a rotary vacuum solvent use Of the same batch 0f rhodium tric'nloride l0 catalyze stripper and a ann ater bath under water aspirator many runs of the reaction. Without this reactivation step, vanum Th di till t i u d i a D 1e-aetone the yield of product is drastically reduced after the initia cold trap. The residue in the stripper is weighed and re run. tained for subsequent use as a catalyst. The collected During a series of runs the catalyst residue grad ally distillate is washed three times with water to remove alcoincreases in weight because 0f the formation Of high-boih K91 and {Q eliminate, excess butadiene The washed ma ing material. It is desirable to remove some of the excess terial is separated, weighed, dried over magnesium sulmaterial from time to time, as, for example, by distilling fate, and 6.02 percent, by weight, of N-phenyl-z-naph. oil, under vacuum, part of the accumulated organic 2O thylarnine is added to stabilize the material. A sample of material. this material is analyzed by vapor phase chromatography It is Within l Of this invention to spsrate the to permit calculation of the yields of individual com process in a continuous manner, as, for example, by c nponents. Separation of the individual components is tinuously introducing moncene and butadiene into a achieved by distillation. In this and in subsequent exactor, which may be a series of reactors in cascade aramplcs the crude net yield is taken as the weight of the rangement, continuously withdrawing reaction mixture, crude product minus the Weight of the dissolved butadiene. distilling Off the diene product, treating the catalyst residue srcent conversion is calculated from this using the with hydrochloric acid and, optionally, ethanol, and co-nformula; tinuously returning the treated catalyst residue to the reactor. at)

The diene compounds which are prepared by the process of this invention are valuable compounds for the preparation of elastomeric polymers. For example, 1,4-hexadiene is useful as a starting material for elastomeric polyvogves digsglvgng 1kg RhC18.3H2O in the Specified amount mars filsclosed U1 2,933,430,; Lihfixadlene, of 95 percent ethanol. Subsequent runs entail mixing of hexadiene, and Z-methyl-IA-hexacllene can be p0lY the catalyst residue which is an oily, red liquid with the lzed to Yield fiim'folmmg materials Whlch tough and stated amounts of 95 percent ethanol and concentrated 63 of tack 1F bakmg- 1 (37 percent) hydrochloric acid. (1 ml. equals 0.012 Representative examples illustrating the present mven- I mglg of HCL) Th5 alcohol and acid solution are not fOuOW- miscible with the catalyst residue and give heterogeneous EXAMFLE 1 mixtures.

The experiments described i hi example are -i d The results of the series of runs using ethylene and out in a one gauon giawlined autoclave equipped h an butadlene reported in Table I show the desirable effects agitator, a gas inlet, a thermocouple well, a discharge leg, of sliding both acid and alcshol t0 the used Catalyst a vent and pressure gauge, and a vacuum inlet. The autoresiduesclave is fitted so that it can be heated or cooled by means The Charge for each fun of this series is 1900 grams of of a jacket through which steam-water mixtures or cool L3-butadisne moles) and 500 grams of ethylene g can b i l d (17.8 moles). The catalyst is prepared by adding 1.0

The general procedure is as follows: The catalyst solugram 0f s' 2 111016) Of 95 p tion used in a given run is charged to the autoclave at 0 Cent ethanol (2110011t 23 grams of ethanol 011 a 100 atmospheric pressure through a fitting on the gas inlet tube Percent basis Whish amounts to about 6050 grams P which is sealed after the addition. The autoclave is then 111016 of y Each fun is Carried Out for minutes cooled to 0 C. or lower by circulating acetone which is at In each run after R1111 the Catalyst usad cogled in a Dry lceq cetone bath in an exfeynal coil is lllfi residue obtained fI'Ol'll the preceding Illl]. t0 VhlCh through the autoclave jacket. The butadiene is charged by has bsefi added the indicaisd number of moles of y distillation into the evacuated autoclave through the gas chloric acid and the indicated amount of ethanol.

weight of crude net. yielclX 100 ti-"eight of (ethylene plus butadiene) Percent conversion Preparation of the catalyst solution for the first run in- Table I H01 Added Crude Ethanol Net Percent Percent Percent Cat. Run Added,'- Yield, Conver- Yield n Yield b Residue,

Mole Mole/mole grams grams sion grams of cat.

0 0 23 827 55.1 43. 8 11.6 72 0 0 23 188 12. 5 11.9 0. 8 75 0 0 23 32 2. l 2. 1 0 64 0 012 3.16 23 643 42. 8 36. 7 6. 5 109 O 012 3. l6 0 255 17. 0 l6. 2 1. 0 116 0. 012 3.16 23 715 47. 7 40.1 7. 9 163 Percent yield of 1,4-hexacliene= b Percent yield of 2,4-hexadicne= Added as 30 ml. of ethanol.

The above table shows that in Runs B and C, when no hydrochloric acid is added to the catalyst residue, the yield falls off sharply. However, in Run D, when 0.012 mole of hydrogen chloride is added to the catalyst residue, the crude net yield increases from 32 grams (Run C) to 643 grams. In Run E, when no ethanol is added to the catalyst residue, the yield again decreases somewhat but increases again in Run F when 0.012 mole of hydrogen chloride and 23 grams of ethanol are added to the catalyst residue.

EXAMPLE 2 A series of runs is carried out in a similar manner to that of Example 1. The catalyst is prepared by adding 1.0 gram of RhCl -3H O (0.0038 mole) to 25 ml. of 95 percent ethanol (about 18.5 grams of ethanol on a 100 percent basis which amounts to about 4870 grams per mole of catalyst). The charge for each run is 1000 grams of butadiene 18.5 moles) and 500 grams of ethylene (17.8 moles). Each run is carried out for 60 minutes at the temperatures shown in Table II.

The product is principally a mixture of 1,4-hexadiene and 2,4-hexadiene having an average composition of 5 moles of 1,4-hexadiene to 1 mole of 2,4-hexadiene.

Table 11 shows the data from the consecutive runs.

Table II H01 Added Ethanol Run Crude Percent Run Added, Temp, Net Conver- M ole/ grams C. Yield, sion Mole mole of grams cat.

e Added as 25 m1. of 95 percent ethanol.

The above Table II shows that 10 runs are carried out with good yields of hexadiene. On the eleventh run, when no hydrochloric acid and no ethanol are added to the catalyst residue from the previous run, the crude yield drops from 613 grams to 35 grams.

EXAMPLE 3 A series of runs is made in a manner similar to that of Example 1 except for difi'erences in amounts of hydrochloric acid, in amounts of ethanol, and in temperature, as indicated in Table III. The grams of ethanol per mole of catalyst correspond to about 3025 (11.5 grams), 4870 (18.5 grams), and 6050 (23 grams).

The product is principally a mixture of 1,4-hexadiene and 2,4-hexadiene having an average composition of about 4 moles of 1,4-hexadiene to 1 mole of 2,4-hexadiene.

Table III HCl Added Ethanol Run Crude Percent Run Added, Temp, Net Conver- Mole/ grams C Yield, sion Mfole mole of grams cat.

B Added as 95 percent ethanol.

6 EXAMPLE 4 A series of runs is carried out by a process similar to that described in Example 1 except that propylene is used instead of ethylene. The catalyst is prepared initially by dissolving 3.0 grams of rhodium trichloride trihydrate in ml. of percent ethanol (about 69 grams of ethanol on a percent basis). The charge for each run is 1000 grams of butadiene (18.5 moles) and 750 grams of propylene (17.8 moles). The temperature range for the runs is 6099 C. Hydrochloric acid and ethanol are added to the catalyst after each run as indicated in Table IV. 69 grams of ethanol corresponds to about 6050 grams per mole of catalyst and 23 grams corresponds to about 2020 grams per mole of catalyst. Data from each run are shown in Table IV.

A series of runs is carried out in a similar manner to that of Example 1. The catalyst is prepared by adding 0.25 gram of RhCl -3H O (0.00095 mole) to 30 m1. of absolute ethanol (about 23.6 grams, approximately 24,840 grams of ethanol per mole of catalyst). An additional 30 ml. of absolute ethanol and hydrochloric acid, as indicated in Table V, are added each time the catalyst residue is recharged to the autoclave. The charge for each run is 1000 grams of butadiene (18.5 moles) and 500 grams of ethylene (17.8 moles). Each run is carried out at the temperature and for the time shown in Table V. The product is principally a mixture of 1,4-hexadiene and 2,4- hexadiene having an average composition of 8.7 moles of 1,4-hexadiene to 1 mole of 2,4-hexadiene. Table V shows the data from the consecutive runs.

Table V H01 Added Run Crude Percent Rim Temp, Time, Net Con- Mole/ 0. minutes Yield, version Mole mole grams of cat.

EXAMPLE 6 A series of runs is made in the following manner: To a 1.5-liter autoclave, equipped with an agitator and lined with polytetrafluoroethylene, is charged a solution of 152 grams (6.2 moles) of ethylene in 304 grams (5.6 moles) of butadiene, together with 0.4 gram of rhodium tn'chloride trihydrate (0.0015 mole) dissolved in 7.7 grams of absolute ethanol to which has been added 0.003 mole of concentrated hydrochloric acid. The reaction mass is ner using the amounts of butadiene and ethylene and the reaction times indicated in Table VII. Table VII shows the data from the series of runs.

Table VII HCl Added Ethanol Added Time at Crude Butadiene Ethylene Reaction Net Percent Run Charged, Charged, Temp, Yield, Convergrams grams Moles/ Gram/ minutes grams S1011 Moles mole of Grams mole of cat. cat.

4, 400 1, 400 1. 07 12. 6 352 4, 150 71 2, 030 35 4, 400 1, 270 0. 28 3. 940 90 2. 568 45. 3 4, 450 l, 270 0. 30 3. 79 040 89 2, 465 43. 1 4, 480 1, 270 0. 3. 5 79 136 2, 737 47. 6 4, 450 l, 270 0. 6O 7. 1 119 1. 400 107 2. 460 43.0 4, 400 1, 400 0. 72 8. 5 158 l, 860 120 3, 086 53. 2 4. 400 1. 180 0.72 8.5 158 1. 860 160 1. 858 33. 3 4, 450 863 1. 20 14. 1 227 2. 670 121 1, 769 33. 3 4, 480 1. 270 0. 7. 1 158 1. 860 127 2, 633 45. 8

agitated and held at a temperature of -85 C. for the times indicated in Table VI. The maximum pressure attained during the reaction is 700 p.s.i.g.

The hexadiene product together with unreacted ethylene, butadiene, and alcohol is separated by vacuum distillation at about mm. Hg and 80 C. from the residue of catalyst salts dissolved in higher boiling hydrocarbon by-products. The hexadienes and some butadiene are condensed and recovered while the ethylene and remaining butadiene are removed as vapor. Ethanol is removed from the hexadienes by washing with water, after which the crude hexadienes are dried and the isomeric 1,4-hexadiene and 2,4-hexadiene are separated by distillation.

At the end of each run the catalyst residue is returned to the reactor. Concentrated hydrochloric acid and, in some cases, ethanol, are added to the residue, and the catalyst is used for the next run. Table VI shows the data from the series of runs.

Table VI [1st series] H01 Added Ethanol Added B Time at Crude Reaction Net Percent Run Temp, Yield, Con- Mole/ Grams] minutes grams version Mole mole Grams mole of of eat. cat.

11.... 003 2 7. 7 5 22 216 36 B 003 2 7. 7 5, 130 21 107 18 C 024 16 3. 8 2 530 26 202 33 D 036 24 0 0 36 141 3 E 060 40 0 0 36 154 25 F 036 24 0 0 50 131 22 G 060 40 0 0 91 104 17 H 060 40 3. 8 2, 530 57 151 25 Ethanol added as ethyl alcohol containing about 2 percent benzene (about 0.77 gram of ethanol per ml.).

EXAMPLE 7 A series of runs is carried out in a S-gallon glass lined autoclave in the following manner:

In the initial run the charge consists of 4400 grams (8.15 moles) of butadiene and 22.3 grams (0.085 mole) of rhodium trichloride trihydrate dissolved in 352 grams of absolute ethanol to which 1.07 moles of concentrated hydrochloric acid has been added. Ethylene is added continuously to maintain a constant reaction pressure of 160 p.s.i.g. The temperature is maintained at 68- 71 C. for 71 minutes. The reaction products are recovered and the percent conversion is calculated, as described in Example 1. After each run the catalyst residue is returned to the reactor, treated with hydrochloric acid and absolute ethanol, and used as the catalyst for the next run.

Each succeeding run is carried out in the same man- It is understood that the preceding examples may be 9 varied, within the scope of the total preceding specification disclosure, by one skilled in the art, to achieve essentially the same results.

As many apparently widely dilferent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for the reactivation of a rhodium trichloride catalyst residue which has become deactivated through use in the preparation of acyclic hydrocarbon dienes having 6 to 7 carbon atoms by condensing a member selected from the group consisting of ethylene and propylene with 1,3-butadiene, said process comprising mixing the resulting catalyst residue with at least one mole of aqueous hydrochloric acid solution per mole of rhodium trichloride catalyst initially charged.

2. A process as defined in claim 1 wherein from about 1.5 to 15 moles of an aqueous hydrochloric acid solution are used per mole of rhodium trichloride catalyst initially charged.

3. A process as defined .in claim 1 wherein ethanol is added concomitant with said mixing step.

4. A process as defined in claim 3 wherein from about 900 to 25,000 grams of ethanol are added per mole of rhodium trichloride.

5. A process for the preparation of acyclic hydrocarbon dienes having 6 to 7 carbon atoms which comprises (I) condensing a member selected from the group consisting of ethylene and propylene with 1,3-butadiene in the presence of a rhodium trichloride catalyst until said catalyst becomes deactivated, (II) isolating the deactivated catalyst residue, (III) mixing the deactivated catalyst residue with at least one mole of aqueous hydrochloric acid solution per mole of catalyst initially charged, and (IV) using the resulting reactivated catalyst residue as a substitute for the catalyst used in step (1) above.

6. A process as defined in claim 5 wherein from about 1.5 to 15 moles of an aqueous hydrochloric acid solution are used in step (HI) per mole of rhodium trichloride catalyst initially charged.

7. A process as defined in claim 5 wherein ethanol is added in step (III).

8. A process as defined in claim 7 wherein from about 900 to 25,000 grams of ethanol are added per mole of rhodium trichloride.

References Cited in the file of this patent UNITED STATES PATENTS ,028 Kuentzel Apr. 5, 1938 ,066 Anderson Dec. 12, 1961 FOREIGN PATENTS 19 France Nov. 9, 1959 

1. A PROCESS FOR THE REACTIVATION OF A RHODIUM TRICHLORIDE CATALYST RESIDUE WHICH HAS BECOME DEACTIVATED THROUGH USE IN THE PREPARATION OF ACYCLIC HYDROCARBON DIENES HAVING 6 TO 7 CARBON ATOMS BY CONDENSING A MEMBER SELECTED FROM THE GROUP CONSISTING OF ETHYLENE AND PROPYLENE WITH 1,3-BUTADIENE, SAID PROCESS COMPRISING MIXING THE RESULTING CATALYST RESIDUE WITH AT LEAST ONE MOLE OF AQUEOUS HYDROCHLORIC ACID SOLUTION PER MOLE OF RHODIUM TRICHLORIDE CATALYST INITIALLY CHARGED. 